664409 has 4 divisors (see below), whose sum is σ = 682404. Its totient is φ = 646416.

The previous prime is 664403. The next prime is 664421. The reversal of 664409 is 904466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 904466 = 2 ⋅452233.

It can be written as a sum of positive squares in 2 ways, for example, as 644809 + 19600 = 803^2 + 140^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-664409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8942 + ... + 9015.

It is an arithmetic number, because the mean of its divisors is an integer number (170601).

2⁶⁶⁴⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

664409 is a deficient number, since it is larger than the sum of its proper divisors (17995).

664409 is a wasteful number, since it uses less digits than its factorization.

664409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17994.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 664409 is about 815.1128756191. The cubic root of 664409 is about 87.2593222717.

The spelling of 664409 in words is "six hundred sixty-four thousand, four hundred nine".